The novel picks up days after the end of the previous volume. The United States is reeling from the Japanese attack of January 12, 1941. President Roosevelt begins his third term with the state goal of defeating Japan, and making the country strong enough to defeat any future enemies.

The titular coup d'état takes place in the U.K. in the Spring of 1941, when group of soldiers, led in part of General Archibald Wavell, arrest Horace Wilson and his Cabinet. Britain then withdraws its forces from the USSR and begins its war with Germany. However, as France does not withdraw from the USSR, Britain is unable to directly engage Germany outside of aerial attacks. Italy, on the other hand, reignites the war with Britain in North Africa.

While France doesn't leave the war with the USSR, it does start resupplying the Spanish Republicans in mid-1941. Word also comes to the French troops in Russia that the Maginot Line is being expanded along the Belgian border.

Meanwhile, the Pacific War between Japan and the Western powers (led by the U.S.) continues to favor Japan, which is able to take several strategic island possessions from France, Britain, and the U.S. In addition, Japan unleashes new biological weapons in China. While the U.S. does make some initial gains early in the year, landing a sizeable force at places like Wake Island, Japan's superior air power effectively undoes America's gains. On the home front, support for the war against Japan is weak. With the war between Britain and Germany renewed, American ships carry supplies to the U.K., while Germany declares unrestricted submarine warfare in the Atlantic.

The novel ends in the closing days of 1941, with France withdrawing from the war with Russia despite Germany's efforts. Germany is now once again facing a two front war. However, the multi-national coalition had advanced deep into Soviet territory before the French withdrawal, and Germany still has Poland, Romania, and other allies. Germany also inserts itself into the North African war between Britain and Italy. Despite repeated pledges by the interim government, the military is still in control in Britain, heightening tensions further among the average Briton. In the Pacific, the American fleet is on the verge of yet another defeat. In Spain, Czech refugee sniper Vaclav Jezek kills Nationalist General Francisco Franco.

In February 2012, Colton Jang posted on reddit.com in hopes of securing a copy of Coup d'Etat early on behalf of his friend, Nachu Bhatnagar. Bhatnagar had been diagnosed with a rare form of cancer, and the treatment was not going well. Bhatnagar was disappointed that he most likely would not live to see the publication of the book.

Jang's efforts were successful, as another author whose work is published at Del Rey saw Jang's post, and connected Jang with editors for the publisher. Nachu Bhatnagar received his copy not long after.[1]